Legendary investor and billionaire George Soros announced Saturday that he is engaged to marry his girlfriend of last four years, Tamiko Bolton.

Considered the seventh richest person in the U.S. with an estimated net worth of $22 billion, according to Forbes, Soros announced his engagement at his 82nd birthday party at his summer home in Southampton, N.Y., Reuters reported.

This will be the third marriage for Soros, and second for Bolton, 40. He has five children from his previous marriages.

Soros won notoriety with a historic trade when he took on the Bank of England and shrewdly bet on a devaluation of the British pound.

In 2011, Soros converted his hedge fund into a family office and stopped managing money for outside investors. However, he continues to be an active contributor to politically liberal causes and frequently addresses world economic events.

Tamiko Bolton previously owned an Internet-based dietary supplement business and is currently running a web-based yoga education business. Bolton holds a master's degree in business from the University of Miami, Reuters added.

"Soros planned a surprise announcement to his assembled friends and family at his birthday party last night. He told them he and Tamiko are engaged and plan to marry next summer in Southampton," a guest told New York Post.

Guests at the party included Blackstone's Byron Wien and the mogul's son Alexander Soros.

The couple reportedly met at a luncheon in New York in 2008 and, "their relationship has developed over time," sources informed the New York Post.

The couple kept a low profile until recently, when the hedge-fund titan was spotted with Bolton in public, in May, at a Paley Center screening of "The Untouchables," New York Post added.

Reportedly, Soros proposed to Bolton during a weekend in his Southampton home. Sources told New York Post that he presented her with a brilliant-cut diamond ring set in platinum on a rose-gold band embedded with pink diamonds.

Responding to a query on pre-nuptial agreement, Soros' attorney William D. Zable told New York Post: "It is well known that Soros will leave the bulk of his estate to charity but he intends to provide generously for his wife."